1. Field of the Invention
This invention relates to a coupled pipe assembly wherein the opposed ends of pipes having an internal coating or lining of corrosion-resistant material are joined by welding. An internal sleeve is used in association with the coupled pipe ends to protect the corrosion-resistant lining of the pipes from heat damage incident to the welding operation.
2. Description of the Prior Art
In various applications, such as in the oil and gas industry, there is a need for alloy pipe, such as steel pipe, provided with a lining of corrosion-resistant material. For this purpose, it is known to bond to the pipe interior various epoxy base materials, polyethylene, polyvinyl chloride, and other thermoplastic and thermosetting materials.
With pipe having internal coatings of materials of this type to provide corrosion resistance, protection must be provided for the coating to prevent deterioration thereof by the heat generated incident to the welding of the pipe ends.
Various assemblies are conventionally employed for this purpose. These assemblies include an internal sleeve having a heat-insulating barrier for positioning adjacent the weld zone of the opposed pipe ends for protection of the corrosion-resistant coating. The interior of the sleeve is provided with a corrosion-resistant coating of the same type as that of the pipe interior. One example of an assembly of this type is disclosed in Kesseler et al. U.S. Patent 3,508,766, issued Oct. 25, 1968.
With prior art assemblies of the type disclosed in the aforementioned patent, it is necessary to provide pipe ends having expanded or belled end portions. This structure is provided so that the sleeve which is provided with mating tapered end portions may be fitted into the pipe ends to support the same in the spaced-apart position required for subsequent welding by deposit of weld material within the space between the pipe ends. With assemblies of this type, the requirement for belling the pipe ends and tapering the ends of the associated sleeve adds significantly to the cost of producing the coupled pipe assembly.
In addition, during assembly, the heat-insulating material adjacent the weld zone may be displaced within the weld zone to impair the welding operation. It is necessary, of course, for the heat-insulating material to be adjacent the weld zone to ensure effective protection of the corrosion-resistant coating from deterioration during welding.